1. Field of the Invention
This invention concerns artificial vascular grafts that provide excellent results in anastomosis, antithrombogenicity and morphology retention.
2. DESCRIPTION OF THE PRIOR ART
Important characteristics for artificial vascular grafts are non-toxicity and non-degradation due to reduction in strength in invivo and the following:
(1) Excellent antithrombotic effect. PA0 (2) Excellent utility for anastomosis. PA0 (3) Excellent morphology retention.
Excellent antithrombogenicity means that the artificial vascular graft forms an intervascular endothelium (a new vascular wall) immediately after implantation.
Conventional artificial vascular grafts are made of woven, knitted or braided polyester fibers which are 1.5 denier or more in fineness.
Conventional artificial vascular grafts are fully and closely interwoven or interknitted to prevent blood leakage through the graft wall and of deformation of the grafts. Consequently, the vascular grafts become very rigid, even though graft softening measures, such as crimping, are taken. This rigidity of the conventional artificial vascular grafts cause a poor penetration of the surgical needle through the graft wall leading to deficiencies which frequently induce a large amount of bleeding in arteriosclerosis.
If the grafts are more loosely woven or braided to improve achievement of anastomosis, the blood leakage becomes severe, especially under administration of anticoagulants.
A further serious problem of conventional grafts is delayed and uneven vascular endothelialization. The thick fibers and dense textures do not provide sites for the endothelialization of such cells. Even when the cells stick to the artificial vascular graft, they are easily washed away due to the dense textural structures. As a result, uniform endothelialization is not produced. In addition, peripheral small vessels are easily obstructed by emboli.
As shown in the Japanese Official Patent Gazette, No. 117287 in 1975; No. 94699 in 1977, and No. 137599 in 1978, loops made on the inner surface of the graft are one way to provide sites for endothelialization. Loops in the conventional grafts, however, provide insufficient sites for cell adhesion, because the loops are fabricated of thick fibers. In addition, the grafts with loops have no satisfactory characteristics for vascular grafts such as ease in penetration of a surgical needle, in anastomosis, satisfactory morphology retention, moderate blood leakage and adaptation to the body. Performing anastomosis and penetration of a surgical needle become difficult when more emphasis is placed on the prevention of blood leakage and morphology retention. When emphasis is placed on functioning in anastomoses and penetration of a surgical needle, prevention of blood leakage and maintenance of the graft shape become difficult. Solving this dilemma has been impossible in the case of conventional vascular grafts.